My computer will place system sounds but not music videos or tutorial lessons from the speakers or with headphones, i have a dell inspiron e 1505 and have check my drivers and it says all it working properly.

Plug in ONLY the regular wired speakers and ONLY to the green port on the back.

Make sure they are powered up and the volume is about half way.

Ok now you need to call up ether the sound card application or preferably the windows volume control from the bottom toolbar.

Click Open Volume Control.

A box with sliders in should appear. make sure that volume control, wave, sw synth, aux, cd player, line in
are all about half way and that none of them have ticks in the box at the bottom.

If any of those are missing click options then properties from the top left and put a tick besides any that were missing (nothing else)
Now close the slider box.

Put a normal music cd in your cd/dvd player on the computer and set it to play with windows media player.
You should now have sound out of the speakers.

Double check that EVERYTHING is ok.
If there is still no sound check the control panle for any hardware issues and rectify those

Sounds like an issue witht he master volume controls